1. Field of the Invention
The present invention relates to a long size image sensor unit and photosensors for use in this sensor unit and a method of manufacturing the photosensors.
2. Description of the Prior Art
Hitherto, in a photoelectric converting apparatus which is used as a photo inputting section of an image information processing apparatus such as a facsimile, a digital copying machine, a character reading apparatus, etc., it is generally well known that a photosensor is used a photoelectric converting element. Particularly, in recent years, there has been adopted an arrangement such that photosensors are one-dimensionally arranged to form a long size line sensor and a highly sensitive image processing apparatus is constituted using this line sensor. As an example of the photosensors constituting such a long size line sensor, there can be mentioned a photoconductive type photosensor of the planar type provided with a pair of electrodes consisting of film-like metal or the like arranged on a photoconductive layer including amorphous silicon (hereinafter, referred to as a-Si (H,X)) or the like containing hydrogen atoms and halogen atoms such as fluorine atoms or the like as a photoconductive material in such a manner that these electrodes face each other so as to form a gap serving as photosensing section.
As a method of manufacturing a-Si (H,X) which constitutes such a photosensor, there are a plasma CVD method, a reactive sputtering method, an ion plating method, etc. In any of these methods, the reaction is facilitated by way of a glow discharge. However, in any of these cases, it is necessary to form the film with a relatively low discharge power to derive the high quality a-Si (H,X) film having a high photoconductivity. However, the photoconductive layer formed by using such a low discharge power has problems such that the adhesive property with a substrate consisting of a glass, ceramics or the like is insufficient and it is likely to cause peel-off of the film when performing the subsequent photolithography process or the like upon formation of the electrode.
Therefore, conventionally, to prevent the peel-off of the film, a method whereby a-Si (H,X) is deposited after the surface of the substrate is made rough has been adopted. Practically speaking, the substrate surface is preliminarily chemically etched by means of, for example, hydrofluoric acid or the like or is physically rubbed using, for instance, a brush or the like. However, such a method has the following drawbacks.
(1) In case of using a chemical such as hydrofluoric acid or the like, the apparatus in the cleaning line becomes complicated and expensive.
(2) It is difficult to control a degree of roughness of the substrate surface.
(3) Micro defects could be easily caused when the substrate surface is made rough and a variation in characteristics is likely to occur because the characteristics of the a-Si (H,X) film which is deposited on those micro defects differ.
Consequently, in case of constituting the long size image sensor using such photosensors as mentioned above, there is a large variation among respective bit signals, so that it is necessary to further provide a correction circuit to correct such a variation and this results in an increase in cost.